In prior optical systems for the viewing of motion pictures (except in the optical system of the inventor's pending U.S. application Ser. No. 222,354), the motion picture film advances intermittently rather than continuously. A frame of the film, motionless, occupies a position centered on the axis of an imaging lens for a period of time. The film is then rapidly advanced until the next frame is brought to this position. This frame, motionless, then occupies this position for a period of time; and so on.
Usually (an exception is the viewing device described in U.S. Pat. No. 3,264,051), the illumination of the film is interrupted by a shutter while the film is advanced.